In underground room and pillar coal mines, the array or pattern of mined areas and remaining unmined coal pillars might, when viewed with X-ray vision from an overhead airplane or helicopter, resemble the squares of a multi-colored chess board. In a typical mine in the United States, about half of the available coal seam is extracted or mined while the other half is left in the remaining coal pillars in order to support the mine roof, i.e., to prevent dangerous roof collapses, and to prevent overhead surface subsidence. This method of mining in the United States accounts for about two-thirds of all underground coal production.
In a conventional mining operation, a miner operator and an assistant are situated on or near a continuous mining machine as coal is being mined and hauled away from the face area. Also, two or more operators are required to haul or transport the mined product away from the face area to an outbye dump station, usually situated hundreds of feet from the mining face. This method of mining features many hazards to the life of coal miners who work underground. These hazards include the following: unsuspected roof falls that can maim or kill miners; methane/coal dust explosions that may be touched off with just one small spark; long-term health effects from breathing fine-sized coal dust; inner ear damage from loud noise pollution in a confined work area; and other general hazards related to heavy mining equipment moving about in confined roadways in an underground mine.
One method of avoiding the above-mentioned problems is to relocate the miners hundreds or perhaps thousands of feet distant from the active and hazardous area being mined. This relocation requires adequate technology to remotely control the face area machinery and the remote reception of the same or similar sensory feedback that the miners currently have while located on or near to heavy mining extraction and coal haulage equipment in the face area. In prior art remote mining machines, the ability to follow a relatively thin seam of coal with any degree of precision is a problem. This lack of precision results in unwanted rock, slate, and shale being cut along with the coal and from which the coal must be later separated. This additional separation adds to the cost of mining coal. Examples of such machines include those disclosed in U.S. Pat. Nos. 4,323,280 (Lansberry et al.); 3,776,592 (Ewing); 4,008,921 (Czauderna et al.); and 4,753,484 (Stolarczyk et al.).
The Lansberry et al. patent discloses a remote mining system used in highwall mines. This mining system incorporates a continuous mining machine, a remote control station, electrical cables for connecting the mining machine with the remote control station, TV cameras, and laser and sonar sensors for keeping the mining machine on a straight line. One disadvantage of this system is that the system will not function in a thin seam mining operation. The reason for this is that because the control station in this system is the size of a house trailer, the system is unable to enter a thin seam mine. Further, although the mining system provides the operator a visual display of the mining face as well as separate information from the laser and sonar sensors, this information is displayed in several different formats, i.e., the video information is displayed on a monitor, the laser information is displayed by a set of lights which indicate direction from a central line, and the sonar information is displayed as an analog read-out. As a result, an operator will have to monitor three different displays with three different formats at the same time.
The Ewing patent discloses a remote mining machine where an operator is located at a launching platform. The operator controls the machine by visual feedback from a set of lights located on the miner. This visual feedback requires the operator to be located near the mining face.
The Czauderna et al. patent discloses an automatic cutter which incorporates isotope test probes to determine the location of the coal rock interface. This depth information is input into a special purpose computer which controls the automatic cutter. This device relies on the coal face being relatively straight and would require direct human intervention to realign the cutter in case of a variation, such as a turn, in the coal face. This device is also restricted by the fact that all the control systems are operated by computer software. Thus, if the system encounters a highly discontinuous or irregular surface, the system will leave behind unmined coal and may also remove some rock. The removal of rock prevents a number of significant safety hazards. These safety hazards range from the possibility of a roof cave-in to the potential for an explosion due to sparks, produced by the cutting of the rock, causing the igniting of ambient coal dust.
The Stolarczyk et al. patent discloses a remotely controlled longwall shearer. The mechanical functions of the shearer are controlled by an operator using a medium frequency transmitter operating in the range from 300-1000 kHz and sending the signal through an alternating current (AC) power cable. A receiver, located on the shearer, receives the transmitted signal and decouples it from the AC power signal. The system provides the operator information on the coal layer thickness by means of a sensor located at the face area of the mine. No visual representation of the coal face is provided.
The following articles provide additional background material on remote mining operations: "Controlling a Thin-Seam Miner 500 feet from the Face", 8th WVU International Mining Electrotechnology Conference, Morgantown W.V., Jul. 30 - Aug. 1, 1986, pp. 80-85; and "Ergonomically-Designed Operator Workstations for a Computer-Aided, Remotely Controlled Mining System", Proceedings International Conference on Ergonomics, Occupational Safety and Health and the Environment, Beijing, China, Oct. 24-28, 1988, pp. 362-373.